3. Craig Kimbrel
Prior to the 2019 season, the Chicago Cubs needed a closer. Aroldis Chapman, Hector Rondon, Wade Davis, and Brandon Morrow had all come and gone by this time (in Morrow's case his arm died). So the Cubs brought in one of the best closers baseball has seen in the 21st century in the form of Craig Kimbrel. Among all active pitchers, Kimbrel has the most saves with an impressive 394. The three-year deal looked pretty solid for both parties, as Kimbrel was set to make $14 million a year, while the Cubs get a lockdown closer. But that's not what happened.
Kimbrel's first season with the Cubs saw him sport a 6.53 ERA in just 23 appearances while giving up a career-high 9 home runs. During his previous 8 seasons, he had never given up that many homers in a given year, but he managed to do it in just 20 innings with Chicago. Injuries and the pandemic only notched him 15 innings in 2020. By the time he finally returned to form in 2021, it was too little too late as the Cubs were set to blow things up at the deadline. Kimbrel was among the stars traded that year, and the Cubs received 2B Nick Madrigal and RHP Codi Heuer from the White Sox for him.